Polymers 2024 , 16 , 110
4of 12
starch solution (3.8%) were added to the mixture with 2 and 5 kg per ton of dry cellulose fibers, respectively. Finally, CaCO 3 and appropriate crosslinkers (SiO 2 , TiO 2 , h-BN, and h-BN-OH) dispersed in PEG solution were introduced to the system. To do so, 1 kg of crosslinkers per 1 ton of dry cellulose fibers was first dispersed in 100 mL of PEG solution and sonicated to obtain a homogeneous mixture. The prepared mixture was mechanically stirred with cellulosic mass for 15 min. Paper sheets were formed using a Rapid-Köthen Automatic Sheet-Forming Machine (Lodz, Poland), following the guidelines of PN-ISO 5262–2. This method of producing modified paper sheets using the mentioned equipment replicates the conditions found in large-scale production, facilitating easy scalability of the entire process. The prepared paper sheets were denoted as reference for the sample without any crosslinker, and PEG/SiO 2 , PEG/TiO 2 , PEG/h-BN, and PEG/h-BN-OH for samples where additional PEG suspension containing SiO 2 , TiO 2 , h-BN, and h-BN-OH were added, respectively. The reference was prepared by the same procedure but without the addition of PEG/inorganic filler mixture. 2.7. Characterization High-resolution transmission electron microscopy (HR-TEM) (Washington, DC, USA) imaging was performed with the FEI Tecnai F20 microscope at an accelerating voltage of 200 kV. The images were taken directly on sample-drop-cast Cu grids with carbon film. A scanning electron microscope (SEM) (VEGA3, TESCAN) (Brno, Czech Republic) was used to determine the morphology of the prepared sheets. The chemical bonding of the structures in the paper sheets was examined using Raman spectroscopy (InVia Renishaw, Wotton-under-Edge, UK) equipped with an excitation wavelength of 785 nm. It is an ideal method to study the structural properties of the nanomaterials. The phase composition was determined by X-ray diffraction (XRD) patterns by using an Aeris (Malvern Panalytical, Malvern, UK) diffractometer using Cu K α radiation. The content of CaCO 3 was determined in accordance with the International Organization of Standardization (ISO 1762:2001). The thermogravimetric analysis was conducted using an SDT Q600 Thermogravimeter (TA Instruments, New Castle, DE, USA) under air flow of 100 mL/min. In each case, the samples were heated from room temperature to 600 ◦ C at a linear heating rate of 10 ◦ C/min. The samples were measured in an alumina crucible with a mass of about 5.0 mg. N2 adsorption/desorption isotherms were acquired at liquid nitrogen temperature (77 K) using a Micromeritics ASAP 2460 (Norcross, GA, USA). The Brunauer–Emmett–Teller (BET) and density functional theory (DFT) methods were adopted to calculate the specific surface area and pore size distribution. 3. Results TEM images of SiO 2 , TiO 2 , h-BN, and h-BN-OH are presented in Figure 1. SiO 2 andTiO 2 reveal distinct morphologies. SiO 2 (Figure 1A) exhibits particles with spherical morphology, showcasing visible porosity within the silica structure. High porosity directly leads to the high surface area of SiO 2 . Similarly, TiO 2 (Figure 1B) nanoparticles display a spherical or quasi-spherical morphology, relative to SiO 2 , and exhibit observable porosity with evident pores. For h-BN, the TEM image illustrates a flat and two-dimensional (2D) sheet-like structure. It is a layered material with a hexagonal lattice resembling graphene, showcasing a thin and planar 2D nature. Hydroxylated h-BN (h-BN-OH, Figure 1D) also portrays this 2D planar structure, with the presence of hydroxyl (OH) groups altering surface characteristics but not the fundamental structural morphology.
Made with FlippingBook Digital Proposal Creator